Smart grid for electric vehicle fleet

Being able to charge up to 30 electric cars at once requires some ingenious energy management. Researchers are incorporating a mix of renewables into the design of a smart grid for Germany’s largest charging station.

The network of charging stations for electric vehicles is becoming more tightly meshed. In Germany, the ratio of electric cars to charging stations is currently two to one and utility companies are pushing forward expansion of charging opportunities, especially in cities and metropolitan areas. Over 2000 charging spots have already been installed nationwide and the country’s largest charging infrastructure is at the Fraunhofer Institute Center Stuttgart IZS – where up to 30 electric vehicles (EVs) at a time can re-charge at AC charge spots in the Fraunhofer Campus parking garage.

There is also one DC fast charging spot that has a charging capacity of up to 50 kilowatts and can fully charge a car’s battery in just 20 minutes. Up to 340 kilowatts of electricity are consumed when all charging spots are occupied – equivalent to around 20 percent of the load of the entire Institute Center, which has a staff of 1500. “Charging an electric vehicle fleet poses high requirements on the energy system. Setting up an EV charging infrastructure of this kind is impossible without smart charging and load management,” says Dipl.-Ing Hannes Rose, head of the Mobility Innovation Lab at the Fraunhofer Institute for Industrial Engineering IAO. Rose and his team are currently using their living lab to investigate the technology required to manage EV fleets. How do you maximize operational efficiency? How do you avoid short circuits occurring during peak load times? How do you design a smart grid that can meet all these requirements? Together with Daimler AG and the Institute for Human Factors and Technology Management at the University of Stuttgart, IAO scientists are developing both the charging infrastructure and the energy management in a project called charge@work.
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